Optical position detection apparatus and display apparatus having position detection function

ABSTRACT

An apparatus for optically detecting an object position includes: position detection light sources irradiating light onto the object; a light guide plate receiving the light and emitting it onto a detection area to form an intensity distribution in the detection area; a light detector having light receiving portions receiving the light reflected by the object; and a signal processing portion detecting the object position based on the intensity distribution, wherein light incident portions receiving the light and side portions except for the light incident portions are provided on outer periphery side portions of the light guide plate, a light emission surface emitting the light incident from the light incident portions toward the detection area is provided on a plane portion of the light guide plate, and at least a portion of the side portions is an anti-reflection surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 13/562,649 filed Jul. 31, 2012, which is a continuation of U.S.application Ser. No. 12/832,344 filed Jul. 8, 2010, now U.S. Pat. No.8,259,309, issued Sep. 4, 2012, which claims priority to Japanese PatentApplication Nos. 2009-178777 filed Jul. 31, 2009 and 2010-060335 filedMar. 17, 2010 all which are hereby expressly incorporated by referenceherein in their entireties.

BACKGROUND

1. Technical Field

The present invention relates to an optical position detection apparatusand a display apparatus having a position detection function that isprovided with the optical position detection apparatus.

2. Related Art

In an electronic appliance such as a portable phone, car navigationsystem, personal computer, ticket machine, bank terminal, or the like, adisplay apparatus having a position detection function, in which a touchpanel is arranged on the front surface of an image generation apparatussuch as a liquid crystal apparatus, has been used recently. In a displayapparatus having the position detection function as described above, aninput of information is performed while an image displayed on the imagegeneration apparatus is referred to. The touch panel as described aboveis composed of a position detection apparatus for detecting the positionof a target object in a detection area.

As detection types of the position detection apparatus, a resistive filmtype, an ultrasonic type, a capacitive type, an optical type, and thelike, are known. The resistive film type is low-cost, but, like thecapacitive type, has low transmissivity. The ultrasonic type or thecapacitive type has a high response speed, but has a low environmentalresistance. In contrast, the optical type has the characteristics ofhigh environmental resistance, high transmissivity, and high responsespeed (see JP-A-2004-295644 and JP-A-2004-303172).

However, optical position detection apparatuses as described inJP-A-2004-295644 and JP-A-2004-303172 require light sources or lightdetectors near the display screen, the number of which corresponds tothe resolution of position coordinates that should be detected, and thusare high-cost.

Accordingly, as schematically illustrated in FIGS. 10A and 10B, theinventor of the present invention is examining an optical positiondetection apparatus in which position detection light sources 12 areinstalled at end portions of a light guide plate 13 to face each other,and a light detector 15 detects a position detection light L2 that isemitted from the light guide plate 13 and reflected by a user's fingerand so on. The optical position detection apparatus as described abovehas the advantages that it can detect the position of the finger and soon with a small number of position detection light sources 12 or lightdetectors 15 if there is a roughly linear relationship between theintensity of the position detection light L2 that is emitted from thelight guide plate 13 and the distance from the position detection lightsource 12.

However, the optical position detection apparatus as illustrated inFIGS. 10A and 10B has a problem that when the position of the finger andso on is actually detected by the optical position detection apparatus,a large error may occur. As a result of examining the problem, theinventor of the present invention has newly found that such an error iscaused by the scattering of the intensity distribution of the positiondetection light L2 in a detection area. That is, since in an area 13 wthat is spaced apart from the position detection light source 12 in alight guide plate 13, the position detection light L2 from the positiondetection light source 12 directly reaches the area 13 w and theposition detection light L2 that is reflected from an outer peripheryside portion of the light guide plate 13 also reaches the area 13 w, thelight emission intensity of the position detection light L2 in the area13 w becomes high in comparison to other areas regardless of the factthat the area 13 w is spaced apart from the position detection lightsource 12. In this case, the configuration as illustrated in FIGS. 10Aand 10B is to explain the problem of the present invention, but does notrefer to related art.

SUMMARY

An advantage of some aspects of the present invention is to provide anoptical position detection apparatus and a display apparatus having aposition detection function that is provided with the optical positiondetection apparatus, which can accurately perform position detectioneven in the case where a position detection method using the intensitydistribution of the position detection light formed by the light guideplate is adopted.

According to an aspect of the invention, there is provided an opticalposition detection apparatus for optically detecting the position of atarget object in a detection area, which includes position detectionlight sources that emit position detection light irradiated onto thetarget object; a light guide plate that receives the position detectionlight therein and emits the received position detection light onto thedetection area to form an intensity distribution of a light emissionquantity of the position detection light in the detection area; a lightdetector having light receiving portions arranged toward the detectionarea to receive the position detection light that is reflected by thetarget object; and a signal processing portion that detects the positionof the target object based on the intensity distribution of the lightemission quantity in the detection area, wherein the light guide plateis configured so that light incident portions for receiving the positiondetection light and side portions except for the light incident portionsare provided on the outer periphery side portions when the light guideplate is seen in a plan view, a light emission surface that emits theposition detection light incident from the light incident portionstoward the detection area is provided on a plane portion when the lightguide plate is seen in a plan view, and at least a portion of the sideportions is an anti-reflection surface that prevents reflection of theposition detection light in the light guide plate.

According to the aspect of the invention, if the position detectionlight that is emitted from a light emission surface of the light guideplate is reflected by a target object that is arranged on the emissionside of the light guide plate, the reflected light is detected by thelight detector. Here, if there is a predetermined correlation betweenthe intensity of the position detection light in the detection area anda distance from the position detection light source, the position of thetarget object can be detected from a light receiving intensity that isobtained through the light detector. Accordingly, it is not necessary toarrange a plurality of optical devices along the detection area, andthus a position detection apparatus with low cost and with low powerconsumption can be configured. Here, in the aspect of the invention, inthe outer periphery side portions of the light guide plate, at least aportion of the side portions except for the light incident portions isthe anti-reflection surface. Accordingly, the light from the positiondetection light sources directly reach the area that is spaced apartfrom the position detection light sources, but by only this, it isdifficult for the light reflected from the outer periphery side portionsof the light guide plate to reach the area. Accordingly, it can beavoided that the light emission intensity of the position detectionlight emitted from the area that is spaced apart from the lightdetection light sources becomes heightened in comparison to that ofother areas. In the aspect of the invention, even in the case where theposition detection method using the intensity distribution of theposition detection light formed by the light guide plate is adopted, theposition detection light is emitted from the light guide plate with anappropriate intensity distribution, and thus the position detection canbe accurately performed.

In the aspect of the invention, it is preferable that the entire surfaceof the side portion is the anti-reflection surface. In thisconfiguration, the reflection of the position detection light can beprevented on the entire outer periphery side portion. Accordingly, sincethe position detection light is emitted from the light guide plate withmore appropriate intensity distribution, the position detection can beperformed more accurately.

In the aspect of the invention, it is preferable that theanti-reflection surface is formed by a light absorption layer formed onthe side portion. In this configuration, it is not necessary to performprocesses that trouble the light guide plate itself, and thus theanti-reflection surface can be easily formed.

When the aspect of the invention is applied to a case in which the lightguide plate is in the form of a tetragonal plane, and the light incidentportions are provided in portions corresponding to corners of thetetragon, a remarkable effect can be obtained. In the case where thelight guide plate is tetragonal and the light incident portions areformed on the portions corresponding to corners of the tetragon, itcannot be avoided that the position detection light is headed toward theouter periphery side portions of the light guide plate. However,according to the aspect of the invention, even in the case of using thelight guide plate as configured above, the position detection light isemitted from the light guide plate with an appropriate intensitydistribution, and thus the position detection can be performed moreaccurately. In the aspect of the invention, the term. “tetragon” means atetragon that further includes a shape in which portions correspondingto corners of the tetragon are cut out.

When the aspect of the invention is applied to a case in which fourposition detection light sources are provided and in the light guideplate, the light incident portions are provided on portions thatcorrespond to the four corners of the tetragon, a remarkable effect canbe obtained. If the above-described configuration is adopted, it cannotbe avoided that the position detection light is headed toward the outerperiphery side portions of the light guide plate. However, according tothe aspect of the invention, even in the case of using the light guideplate as configured above, the position detection light is emitted fromthe light guide plate with an appropriate intensity distribution, andthus the position detection can be performed more accurately.

When the aspect of the invention is applied to a case in which twoneighboring position detection light sources among four positiondetection light sources simultaneously emit the position detectionlight, a remarkable effect can be obtained. If the above-describedconfiguration is adopted, it cannot be avoided that the positiondetection light is headed toward the outer periphery side portions ofthe light guide plate. However, according to the aspect of theinvention, even in the case of using the light guide plate as configuredabove, the position detection light is emitted from the light guideplate with an appropriate intensity distribution, and thus the positiondetection can be performed more accurately.

The optical position detection apparatus according to the aspect of theinvention may be used to configure a display apparatus having a positiondetection function. In this case, the display apparatus having theposition detection function has an image generation apparatus that formsan image in an overlapping area when the light guide plate is seen in aplan view. Examples of the image generation apparatus may be aprojection display apparatus or a direct-view display apparatus, such asa liquid crystal apparatus, an organic electroluminescence apparatus, orthe like.

The display apparatus having the position detection function accordingto the aspect of the invention may be used in an electronic appliance,such as a portable phone, car navigation system, personal computer,ticket machine, bank terminal, or the like, in addition to various kindsof display apparatuses.

According to another aspect of the invention, there is provided anoptical position detection apparatus for optically detecting a positionof a target object, which includes a light guide plate having lightincident portions provided on four corner portions of an outer peripheryportion; four position detection light sources that emit positiondetection light toward the light incident portions; a light detectorthat receives the position detection light which is emitted from onesurface in a thickness direction of the light guide plate and isreflected by the target object; and a signal processing portion thatdetects the position of the target object based on the result of lightreceived in the light detector, wherein the four position detectionlight sources emit the position detection light through alternatelight-up by changing a combination of one portion of the positiondetection light sources and the other portion of the position detectionlight sources the number of which is equal to that of the one portion ofthe position detection light sources, and at least a portion of theouter periphery portions of the light guide plate except for the lightincident portions is an anti-reflection surface that prevents reflectionof the position detection light in the light guide plate.

According to this aspect of the invention, when the position detectionlight that is emitted from one side surface (a light emission surface)in a thickness direction of the light guide plate is reflected by atarget object that is arranged on the emission side of the light guideplate, the reflected light is detected by the light detector. Here, ifthere is a predetermined correlation between the intensity of theposition detection light in the detection area and the distance from theposition detection light source, a position of the target object can bedetected from a light receiving intensity that is obtained through thelight detector. Accordingly, it is not necessary to arrange a pluralityof optical devices along the detection region, and thus a positiondetection apparatus with low cost and with low power consumption can beconfigured. Here, in this aspect of the invention, in the outerperiphery portions of the light guide plate, at least a portion in whichthe position detection light sources are not arranged is theanti-reflection surface. Accordingly, the light from the positiondetection light sources directly reach the area that is spaced apartfrom the position detection light sources, but it is difficult for thelight reflected from the outer periphery portions of the light guideplate to reach the area. Accordingly, it can be avoided that the lightemission intensity of the position detection light emitted from the areathat is spaced apart from the light detection light sources becomesheightened in comparison to that of other areas. In this aspect of theinvention, even in the case where the position detection method usingthe intensity distribution of the position detection light formed by thelight guide plate is adopted, the position detection light is emittedfrom the light guide plate with an appropriate intensity distribution,and thus the position detection can be accurately performed.

In this aspect of the invention, it is preferable that in the outerperiphery portions of the light guide plate, the entire portion in whichthe position detection light sources are not arranged is theanti-reflection surface. In this configuration, the reflection of theposition detection light can be prevented in the entire portion in whichthe position detection light sources are not arranged among the outerperiphery portions of the light guide plate. Accordingly, the positiondetection light can be emitted from the light guide plate with moreappropriate intensity distribution, and thus the position detection canbe performed more accurately.

In this aspect of the invention, the anti-reflection surface may adopt aconfiguration that is formed by a light absorption layer formed on theouter periphery portions of the light guide plate.

In this aspect of the invention, the outer periphery portions of thelight guide plate may include the light incident portions provided onfour corner portions thereof, and the light detector may adopt aconfiguration in which the light detector is arranged in an overlappingposition in the thickness direction of the light guide plate with thecenter of the side portion that is interposed between the neighboringtwo corner portions among the four corner portions.

In this aspect of the invention, it is preferable that the positiondetection light is composed of infrared rays. In this case, the positiondetection light is not visually recognized.

The optical position detection apparatus according to the aspects of theinvention can be used in a projection display apparatus having aposition detection function. In this case, the light guide plate adoptsa configuration in which one surface thereof crosses a direction inwhich the image is projected. Also, the projection display apparatushaving the position detection function has the optical positiondetection apparatus according to the aspect of the invention and animage projection apparatus that projects the image.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIGS. 1A and 1B are explanatory views schematically illustrating aconfiguration of an optical position detection apparatus to which theinvention is applied and a display apparatus having a position detectionfunction that is provided with the optical position detection apparatus.

FIGS. 2A to 2C are explanatory views illustrating a detailedconfiguration of the optical position detection apparatus to which theinvention is applied.

FIGS. 3A and 3B are explanatory views illustrating the contents ofsignal processing in the optical position detection apparatus to whichthe invention is applied and the display apparatus having the positiondetection function.

FIG. 4 is a plan view of a light guide plate that is used in an opticalposition detection apparatus to which the invention is applied and adisplay apparatus having a position detection function.

FIG. 5 is an exploded perspective view of an optical position detectionapparatus according to a modified example 1 of the invention.

FIG. 6 is an explanatory view illustrating a cross-sectionalconfiguration of an optical position detection apparatus according to amodified example 1 of the invention.

FIG. 7 is an exploded perspective view of an optical position detectionapparatus according to a modified example 2 of the invention.

FIG. 8 is an explanatory view illustrating a cross-sectionalconfiguration of an optical position detection apparatus according to amodified example 2 of the invention.

FIGS. 9A to 9C are explanatory views illustrating an electronicappliance using a display apparatus having position detection functionaccording to an aspect of the invention.

FIGS. 10A and 10B are explanatory views illustrating a basicconfiguration of an optical position detection apparatus.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, embodiments of the invention will be described in detailwith reference to the accompanying drawings.

Configurations of an Optical Position Detection Apparatus and a DisplayApparatus Having a Position Detection Function the Entire Configurationof a Display Apparatus Having a Position Detection Function

FIGS. 1A and 1B are explanatory views schematically illustrating aconfiguration of an optical position detection apparatus to which theinvention is applied and a display apparatus having a position detectionfunction that is provided with the optical position detection apparatus.Specifically, FIGS. 1A and 1B are an explanatory view illustrating aconfiguration example in the case of using a projection displayapparatus that projects an image from the front (input manipulationside) with respect to an image projection surface, and an explanatoryview illustrating a configuration example in the case of using aprojection display apparatus that projects an image from the rear(opposite side to the input manipulation side) with respect to the imageprojection surface.

A display apparatus 100 having a position detection function asillustrated in FIGS. 1A and 1B is provided with an optical positiondetection apparatus 10 and an image generation apparatus 200. When atarget object Ob such as a finger approaches a detection area 10R, theoptical position detection apparatus 10 detects the plane position ofthe target object based on an image that is displayed by the imagegeneration apparatus 200.

Specifically, as described later, the optical position detectionapparatus 10 is provided with position detection light sources 12 thatemit the position detection light, a light guide plate 13, and a lightdetector 15 having a light receiving portion 15 a that faces on thedetection area 10R.

In this embodiment of the invention, the image generation apparatus 200is of a projection type, and has a screen-shaped projected surface 201that is arranged to overlap the front surface side (input manipulationside) of the light guide plate 13. Also, the front surface (one surfacein the thickness direction) of the light guide plate 13 and theprojected surface 201 cross the projection direction of an image fromthe image generation apparatus 200. Due to this, the image generationapparatus 200 forms an image in an overlapping area when the light guideplate 13 is seen in a plan view. In this embodiment of the invention, animage forming area 20R is an area that substantially overlaps thedetection area 10R of the optical position detection apparatus 10. Here,the projected surface 201 is made of a material that can transmitinfrared rays such as white light and so on.

In the display apparatus 100 having the position detection function asillustrated in FIGS. 1A and 1B, the image generation apparatus 200 ofthe display apparatus 100 having the position detection function asillustrated in FIG. 1A is provided with a projection display apparatus203 that projects an image from the front (input manipulation side). Theimage generation apparatus 200 of the display apparatus 100 having theposition detection function as illustrated in FIG. 1B is provided with amirror 206 arranged in the rear (the opposite side to the inputmanipulation side) of the light guide plate 13 and the projected surface201, and a projection display apparatus 207 that projects an imagetoward the mirror 206.

Detailed Configuration of an Optical Position Detection Apparatus 10

FIGS. 2A to 2C are explanatory views illustrating a detailedconfiguration of the optical position detection apparatus to which theinvention is applied. Specifically, FIGS. 2A, 2B, and 2C are anexplanatory view schematically illustrating a cross-sectionalconfiguration of the optical position detection apparatus, anexplanatory view illustrating a configuration of a light guide plate andso on that is used in the optical position detection apparatus, and anexplanatory view illustrating an attenuation state of the positiondetection infrared rays in the light guide plate.

As illustrated in FIGS. 2A and 2B, in the optical position detectionapparatus 10 according to this embodiment of the invention, the lightguide plate 13 is in the form of a tetragon or briefly in the form of atetragonal plane. Accordingly, the optical position detection apparatus10 is provided with four position detection light sources 12A to 12D(the position detection light sources 12 as illustrated in FIGS. 1A and1B) that emit position detection light L2 a to L2 d, the light guideplate 13 having four light incident portions 13 a to 13 d which areprovided on a surrounding outer periphery side portion 13 m of the lightguide plate and to which the position detection light L2 a to L2 d isincident, and the light detector 15 that faces the light receivingportion 15 a in the detection area 10R. The light guide plate 13 has alight emission surface 13 s provided on one surface (upper surface asillustrated) to emit the position detection light L2 a to L2 d havingpropagated through the inside of the light guide plate 13, and the lightemission surface 13 s and the outer periphery side portion 13 m areorthogonal to each other. That is, when the light guide plate 13 is seenin a plan view, one surface of the light guide plate 13 in the thicknessdirection becomes the light emission surface 13 s, and the outerperiphery portion thereof in the thickness direction becomes the outerperiphery side portion 13 m that is orthogonal to the light emissionsurface 13 s.

In this embodiment of the invention, the four position detection lightsources 12A to 12D and the four light incident portions 13 a to 13 d areall installed in positions that correspond to the corners 13 e, 13 f, 13g, and 13 h of the light guide plate 13. Accordingly, the outerperiphery side portion 13 m, when the light guide plate 13 is seen in aplan view, is provided with the light incident portions 13 a to 13 dthat receive the position detection light L2 a to L2 d and side portions13 i, 13 j, 13 k, and 13 l other than the light incident portions 13 ato 13 d. The light incident portions 13 a to 13 d, for example, areconfigured by sectional surfaces formed by removing the corner portionsof the light guide plate 13. The position detection light sources 12A to12D are arranged to face the light incident portions 13 a to 13 d, andpreferably, are arranged to close contact to the light incident portions13 a to 13 d. In this embodiment of the invention, a compensation lightdetector 15 x is used in addition to the light detector 15. Thecompensation light detector 15 x is to compensate for the influence of atemperature or the like upon the result of detection that is obtainedthrough the light detector 15 rather than to detect the positiondetection light L2 a to L2 d.

The light guide plate 13 is formed of a transparent resin plate such aspolycarbonate or acrylic resin. On the light emission surface 13 s ofthe light guide plate 13 or the rear surface 13 t that is opposite tothe light emission surface 13 s, a surface concavo-convex structure, aprism structure, a scattering layer (not illustrated), and the like, areinstalled. By such a light scattering structure, the light, which areincident from the light incident portions 13 a to 13 d and propagatethrough the inside of the light guide plate, are gradually deflected asthey travel in their propagation directions, and then are emitted fromthe light emission surface 13 s. In this case, on the light emissionside of the light guide plate 13, optical sheets such as a prism sheet,alight scattering plate, and the like, may be arranged to seek theuniformity of the position detection light L2 a to L2 d, if necessary.

The position detection light sources 12A to 12D are composed of lightemitting devices, for example, such as LEDs (Light Emitting Diodes), andemit the position detection light L2 a to L2 d composed of infrared raysin accordance with drive signals output from a driving circuit (notillustrated). The type of the position detection light L2 a to L2 d isnot specially limited, but it is preferable that they have a wavelengthdistribution that is different from that of visible light, or they havedifferent light emitting features through the addition of modulationsuch as flickering thereto. Also, it is preferable that the positiondetection light L2 a to L2 d have a wavelength area which can beefficiently reflected by a target object Ob such as a finger or a touchpen. Accordingly, if the target object Ob is part of a human body suchas a finger and so on, it is preferable that the position detectionlight may be infrared rays (especially, near infrared rays that is nearto the visible light region, for example, having a wavelength in theneighborhood of 850 nm) having a high reflection rate on the surface ofthe human body or may have the wavelength of 950 nm. Also, if theposition detection light L2 is the infrared rays, it has the advantagethat the position detection light L2 is not visually recognized.

Basically, a plurality of position detection light sources 12A to 12D isinstalled, and emits the position detection light L2 a to L2 d indifferent positions, respectively. Among the four position detectionlight sources 12A to 12D, the position detection light sources indiagonal positions form a pair to constitute a first light source, andother two position detection light sources form a pair to constitute asecond light source. Also, among the four position detection lightsources 12A to 12D, two neighboring position detection light sources mayform a pair to constitute a first light source pair, and other twoposition detection light sources may form a pair to constitute a secondlight source pair.

In the display apparatus 100 having the position detection function asconfigured above, the position detection light L2 a and the positiondetection light L2 b propagate in opposite directions as indicated byarrows A within the light guide plate 13, and are emitted from the lightemission surface 13 s. Also, the position detection light L2 c and theposition detection light L2 d propagate in opposite directions thatcross the directions as indicated by the arrows A (directions indicatedby arrows B), respectively, and are emitted from the light emissionsurface 13 s.

The detection area 10R is a plane range in which the position detectionlight L2 a to L2 d is emitted to the visually recognizable side(manipulation side) and in which reflected light due to the targetobject Ob may occur. In this embodiment of the invention, the planeshape of the detection area 10R is a tetragon, and the light detector 15is arranged roughly in the center portion in the length direction of onelong-side portion among four side portions of the detection area. Thatis, the light detector 15 is arranged in an overlapping position in thethickness direction of the light guide plate 13 with respect to the sideportion 13 l that is inserted between the neighboring corner portions(optical incident portions 13 b and 13 d) in the light guide plate 15.In the detection area 10R, the inside angle of the corner portions ofthe neighboring sides is set to 90 degrees, and this inside angle isequal to the inside angle of the corner portions 13 e to 13 h of thelight guide plate 13.

Basic Principle

A method of acquiring position information of the target object Ob basedon the detection of the light detector 15 will be described. Variousposition information acquisition methods may be considered, and as oneexample of such methods, for example, a method of obtaining positioncoordinates in a direction in which two corresponding light sources areconnected may be performed by obtaining the ratio of attenuationcoefficients of two position detection light based on the ratio of thedetected light quantities of the position detection light and obtainingpropagation distances of both the position detection light from theratio of the attenuation coefficients.

First, in a display apparatus 100 having a position detection functionaccording to an embodiment of the invention, position detection light L2a to L2 d emitted from the position detection light sources 12A to 12Dare incident from light incident portions 13 a to 13 d to the inside ofa light guide plate 13, travel within the light guide plate 13, and aregradually emitted from a light emission surface 13 s. As a result, theposition detection light L2 a to L2 d is emitted in the form of asurface from the light emission surface 13 s.

For example, the position detection light L2 a from the light incidentportion 13 a travels within the light guide plate 13 toward the lightincident portion 13 b, and is gradually emitted from the light emissionsurface 13 s. In the same manner, the position detection light L2 c andL2 d travel within the light guide plate 13, and are gradually emittedfrom the light emission surface 13 s. Accordingly, if a target object Obsuch as a finger is arranged in the detection area 10R, the positiondetection light L2 a to L2 d is reflected by the target object Ob, and aportion of the reflected light is detected by the light detector 15.

Here, the light quantity of the position detection light L2 a that isemitted onto the detection area 10R is linearly attenuated according tothe distance from the position detection light source 12A as indicatedas a solid line in FIG. 2C, and the light quantity of the positiondetection light L2 b that is emitted onto the detection area 10R islinearly attenuated according to the distance from the positiondetection light source 12B as indicated as a dotted line in FIG. 2C.

Also, if it is assumed that the control amount (e.g. current amount),conversion coefficient, and light emission quantity of the positiondetection light source 12A are Ia, k, and Ea, and the control amount(e.g. current amount), conversion coefficient, and light emissionquantity of the position detection light source 12B are Ib, k, and Eb,the following is realized.

Ea=k·Ia

Eb=k·Ib

Also, if it is assumed that the attenuation coefficient and detectedlight quantity of the position detection light L2 a are fa and Ga, andthe attenuation coefficient and detected light quantity of the positiondetection light L2 b are fb and Gb, the following is realized.

Ga=fa·Ea=fa·k·Ia

Gb=fb·Eb=fb·k·Ib

Accordingly, if it is assumed that Ga/Gb, which is the ratio of detectedlight quantities of both the position detection light, can be detectedin the light detector 15, the following is realized.

Ga/Gb=(fa·Ea)/(fb·Eb)=(fa/fb)·(Ia/Ib)

Accordingly, if values that correspond to the ratio of light emissionquantities Ea/Eb and the ratio of control amounts Ia/Ib are known, theratio of attenuation coefficients fa/fb can also be known. If there is alinear relationship between the ratio of the attenuation coefficientsand the ratio of traveling distances of both the position detectionlight, position information of the target object Ob can be obtainedthrough pre-setting of the linear relationship.

As a method of obtaining the ratio of the attenuation coefficientsfa/fb, for example, the position detection light source 12A and theposition detection light source 12B are turned on and off in reversephase (for example, square wave or sine wave drive signals are operatedto have a phase difference of 180° at a frequency where the phasedifference due to the difference between the traveling distances can bedisregarded), and then the waveforms of the detected light quantitiesare analyzed. More realistically, for example, the control amount Ia ofone side is fixed (Ia=Im), the control amount Ib of the other side iscontrolled so that the detected waveform is unable to be observed, thatis, so that the ratio of detected light quantities Ga/Gb becomes “1”,and the ratio of attenuation coefficients fa/fb is derived from thecontrol amount Ib=Im·(fa/fb) at that time.

Also, the following is realized so that the sum of the control amountsis constant.

Im=Ia+Ib

In this case, since the following equation is satisfied,

Ib=Im·fa/(fa+fb)

fa/(fa+fb)=α,

the ratio of attenuation coefficients is obtained by the followingequation.

fa/fb=α/(1−α)

Accordingly, the position information in a direction indicated by anarrow A of the target object Ob can be acquired by driving the positiondetection light source 12A and the position detection light source 12Bin reverse phase. Also, the position information in a directionindicated by an arrow B of the target object Ob can be acquired bydriving the position detection light source 12C and the positiondetection light source 12D in reverse phase. Accordingly, in the controlsystem, the position coordinates on the XY plane of the target object Obcan be acquired by sequentially performing the detection operation indirections A and B. That is, according to the optical position detectionapparatus 10 in this embodiment, the position coordinates on the XYplane of the target object Ob is acquired by emitting the positiondetection light through an alternative light-up by changing thecombination of the position detection light sources of one portion andthe position detection light sources of the other portion with the samenumber among four position detection light sources 12A to 12D.

As described above, in acquiring the plane position information insidethe detection area 10R of the target object Ob based on the ratio oflight quantities of the position detection light detected by the lightdetector 15, a microprocessor unit (MPU) is used as the signalprocessing portion, and accordingly, a configuration that performsprocessing according to the execution of predetermined software(operation program) may be adopted. Also, to be described later withreference to FIGS. 3A and 3B, a configuration in which a signalprocessing portion using hardware such as a logic circuit performs theprocessing may be adopted. The signal processing portion may be insertedas apart of a display apparatus 100 having the position detectionfunction, or may be configured inside an electronic appliance on whichthe display apparatus 100 having the position detection function ismounted.

Configuration Example of a Signal Processing Portion

FIGS. 3A and 3B are explanatory views illustrating the contents ofsignal processing in the optical position detection apparatus 10 towhich the invention is applied and the display apparatus 100 having theposition detection function. FIGS. 3A and 3B are explanatory viewsillustrating the optical position detection apparatus 10 to which theinvention is applied and the display apparatus 100 having the positiondetection function and the contents of processing in a light emittingintensity compensation command portion of the signal processing portion.

As illustrated in FIG. 3A, in the optical position detection apparatus10 and the display apparatus 100 having the position detection functionaccording to this embodiment, a position detection light source drivingcircuit 110 applies a drive pulse to the position detection light source12A through a variable resistor 111, and applies a drive pulse to theposition detection light source 12B through an inversion circuit 113 anda variable resistor 112. Accordingly, the position detection lightsource driving circuit 110 modulates position detection light L2 a andL2 b by applying an inverse drive pulse to the position detection lightsource 12A and the position detection light source 12B, and emits themodulated position detection light. Also, a common light detector 15receives the light which is the position detection light L2 a and L2Breflected from a target object Ob. In a light intensity signalgeneration circuit 140, a resistor 15 r of about 1 kΩ is electricallyconnected in series to the light detector 15, and a bias voltage Vb isapplied to both end terminals thereof.

In the light intensity signal generation circuit 140, a signalprocessing portion 150 is electrically connected to a connection pointP1 of the light detector 15 and the resistor 15 r. A detection signal Vcoutput from the connection point P1 of the light detector 15 and theresistor 15 r is indicated by the following equation.

Vc=V15 (V15+resistance value of the resistor 15r)

Here, V15 is an equivalent resistance of the light detector 15.

Accordingly, if a case where an environmental light is not incident tothe light detector 15 and a case where an environmental light isincident to the light detector 15 are compared with each other, thelevel and the amplitude of the detection signal Vc become greater in thecase where the environmental light is incident to the light detector 15.

The signal processing portion 150 is briefly provided with a positiondetection signal extraction circuit 190, a position detection signalseparation circuit 170, and a light emitting intensity compensationcommand circuit 180.

The position detection signal extraction circuit 190 is provided with afilter 192 composed of a capacitor of about 1 nF, and this filter 192functions as a high-pass filter that removes a DC component from thesignal output from the connection point P1 of the light detector 15 andthe resistor 15 r. Accordingly, by the filter 192, the positiondetection signal Vd of the position detection light L2 a and L2 b by thelight detector 15 is extracted from the detection signal Vc output fromthe connection point P1 of the light detector 15 and the resistor 15 r.That is, since the environmental light can be considered to have aconstant intensity in a certain period in comparison to the modulatedposition detection light L2 a and L2 b, a low-frequency component or theDC component due to the environmental light is removed by the filter192.

Also, the position detection signal extraction circuit 190 has anaddition circuit 193 that is provided with a feedback resistor 194 ofabout 220 kΩ at the rear end of the filter 192, and the positiondetection signal Vd extracted by the filter 192 is output to theposition detection signal separation circuit 170 as a position detectionsignal Vs which overlaps a voltage V/2 that is ½ of the bias voltage Vb.

The position detection signal separation circuit 170 is provided with aswitch 171 that performs a switching operation in synchronization with adrive pulse that is applied to the position detection light source 12A,a comparator 172, and a capacitor 173 that is electrically connected toinput lines of the comparator 172. Accordingly, if the positiondetection signal Vs is input to the position detection signal separationcircuit 170, an effective value Vea of the position detection signal Vsin a period when the position detection light L2 a lights up and aneffective value Veb of the position detection signal Vs in a period whenthe position detection light L2 b lights up are alternately output fromthe position detection signal separation circuit 170 to the lightemitting intensity compensation command circuit 180.

The light emitting intensity compensation command circuit 180 performs aprocess as illustrated in FIG. 3B by comparing the effective values Veaand Veb, and outputs a control signal Vf to the position detection lightsource driving circuit 110 so that the effective value Vea of theposition detection signal Vs in a period when the position detectionlight L2 a lights up and the effective value Veb of the positiondetection signal Vs in a period when the position detection light L2 blights up become the same level. That is, the light emitting intensitycompensation command circuit 180 compares the effective value Vea of theposition detection signal Vs in a period when the position detectionlight L2 a lights up and the effective value Veb of the positiondetection signal Vs in a period when the position detection light L2 blights up with each other, and if they are the same value, the lightemitting intensity compensation command circuit 180 maintains thedriving condition of the current state of the position detection lightsources 12A and 12B. In contrast, if the effective value Vea of theposition detection signal Vs in a period when the position detectionlight L2 a lights up is lower than the effective value Veb of theposition detection signal Vs in a period when the position detectionlight L2 b lights up, the light emitting intensity compensation commandcircuit 180 heightens the light emission quantity of the positiondetection light source 12A by lowering the resistance value of thevariable resistor 111. Also, if the effective value Veb of the positiondetection signal Vs in a period when the position detection light L2 blights up is lower than the effective value Vea of the positiondetection signal Vs in a period when the position detection light L2 alights up, the light emitting intensity compensation command circuit 180heightens the light emission quantity of the position detection lightsource 12B by lowering the resistance value of the variable resistor112.

By doing this, in the optical position detection apparatus 10 and thedisplay apparatus 100 having the position detection function, the lightemitting intensity compensation command circuit 180 of the signalprocessing portion 150 controls the control amount (current amount) ofthe position detection light sources 12A and 12B so that the detectionamounts of the position detection light L2 a and L2 b, which is detectedby the light detector 15, become equal to each other. Accordingly, thelight emitting intensity compensation command circuit 180 outputs to theposition determination portion 120 information regarding the controlamounts of the position detection light sources 12A and 12B so that theeffective value Vea of the position detection signal Vs in a period whenthe position detection light L2 a lights up and the effective value Vebof the position detection signal Vs in a period when the positiondetection light L2 b lights up become the same level, as the positiondetection signal Vg, and thus the position determination portion 120 canobtain the position coordinates in a direction indicated by an arrow Aof the target object Ob in the detection area 10R. Also, using the sameprinciple, the position determination portion can obtain the positioncoordinates in a direction indicated by an arrow B of the target objectOb in the detection area 10R. Accordingly, the position determinationportion can acquire the position coordinates in an XY plane of thetarget object Ob.

Also, in this embodiment of the invention, in the position detectionsignal extraction circuit 190, the filter 192 extracts the positiondetection signal Vd by removing the DC component which is caused by theenvironmental light from the detection signal Vc output from theconnection point P1 of the light detector 15 and the resistor 15 r.Accordingly, even in the case where the detection signal Vc output fromthe connection point P1 of the optical detector 15 and the resistor 15 rincludes a signal component which is caused by an infrared component ofthe environmental light, the influence of the environmental light can becancelled.

Other Position Detection Methods

In the optical position detection apparatus 10 in this embodiment, thefollowing configuration may be adopted in addition to theabove-described configuration, in which the four position detectionlight sources 12A to 12D emit the position detection light throughalternate light-up by changing a combination of one portion of theposition detection light sources and the other portion of the positiondetection light sources the number of which is equal to that of the oneportion of the position detection light sources. That is, in the opticalposition detection apparatus 10 in this embodiment of the invention, theposition detection light for detecting the position in a first direction(X direction) may be generated by driving the position detection lightsources 12A and 12D in phase, driving the position detection lightsources 12B and 12C in phase, and driving the position detection lightsources 12A and 12D and the position detection light sources 12B and 12Cin reverse phase. In this case, in another timing, the positiondetection light for detecting the position in a second direction (Ydirection) may be generated by driving the position detection lightsources 12A and 12C in phase, driving the position detection lightsources 12B and 12D in phase, and driving the position detection lightsources 12A and 12C and the position detection light sources 12B and 12Din reverse phase. Even in this method, the position coordinates on theXY plane of the target object Ob can be acquired. According to theconfiguration whereby a plurality of position detection light sourceslight up simultaneously, for example, the contrast inclinationdistribution of the position detection light is appropriately obtainedin a wider region than that of the configuration whereby one positiondetection light source lights up, and thus more accurate positiondetection becomes possible. Also, in the case of performing the positiondetection in a long-side direction of the light guide plate 13(detection region 10R), the position detection in the long-sidedirection is performed based on the difference in results of detectionby the light detector 15 between the period in which the positiondetection light sources 12A and 12D light up and the period in which theposition detection light sources 12B and 12C light up. Also, in the caseof performing the position detection in a short-side direction of thelight guide plate 13 (detection region 10R), the position detection inthe short-side direction is performed based on the difference in resultsof detection by the light detector 15 between the period in which theposition detection light sources 12A and 12C light up and the period inwhich the position detection light sources 12B and 12D light up. Even bythis method, the influence of the environmental light can be cancelled.Also, if the intensity distribution as illustrated in FIG. 2Ccorresponds to simple increase or simple decrease, the positiondetection can be performed even in the case where there is no linearrelationship.

Also, the position of the target object Ob in the Z-axis direction maybe detected by making all of the four position detection light sources12A to 12D light up.

Detailed Configuration of a Light Guide Plate

FIG. 4 is a plan view illustrating the light guide plate 13 that is usedin the optical position detection apparatus 10 to which the invention isapplied and the display apparatus 100 having the position detectionfunction.

The optical position detection apparatus 10 according to an embodimentof the invention is on the assumption that there is a predeterminedcorrelation between the intensity of the position detection light L2 ato L2 d emitted from the light guide plate 13 and the distance from theposition detection light sources 12A to 12D. However, if a difference inintensity distribution occurs, which has been explained with referenceto FIG. 10B, the detection accuracy is deteriorated.

Accordingly, in the embodiment of the invention, as illustrated in FIGS.2B and 4, at least a portion of the outer periphery side portion 13 m ofthe light guide plate 13, except for the light incident portions 13 a to13 d, becomes an anti-reflection surface 13 v. In this embodiment of theinvention, the entire surface of the side portions 13 i, 13 j, 13 k, and13 l, except for the light incident portions 13 a to 13 d, among theouter periphery side portion 13 m of the light guide plate 13 becomes ananti-reflection surface 13 v, and the entire surface of the outerperiphery side portion 13 m of the light guide plate 13 except for thelight incident portions 13 a to 13 d becomes the anti-reflection surface13 v.

In forming the anti-reflection surface 13 v, in this embodiment of theinvention, a light absorption layer 14, which is a black metal layersuch as chrome or a black film, is laminated on the side portions 13 i,13 j, 13 k, and 13 l of the section surface 13 m.

Accordingly, as illustrated in FIG. 4, the light headed toward the sideportions 13 i, 13 j, 13 k, and 13 l (anti-reflection surface 13 v) amongthe position detection light L2 a to L2 d incident from the lightincident portions 13 a to 13 d in the light guide plate 13 are absorbedby the light absorption layer 14, and are not reflected.

Primary Effects of the Embodiment

As described above, in the optical position detection apparatus 10according to this embodiment and the display apparatus 100 having theposition detection function, if the position detection light L2 a to L2d is emitted from the light emission surface 13 s of the light guideplate 13 and are reflected by the target object Ob arranged on theemission side of the light guide plate 13, the reflected light isdetected by the light detector 15. Here, if there is a predeterminedcorrelation between the intensity of the position detection light L2 ato L2 d in the detection area 10R and the distance from the positiondetection light sources 12A to 12D, the position of the target object Obcan be detected from the light receiving intensity obtained through thelight detector 15. Accordingly, it is not necessary to arrange aplurality of light elements along the detection region 10R, and thus theposition detection apparatus 10 with low cost and with low powerconsumption can be configured.

Here, in this embodiment of the invention, the outer periphery portion13 m except for the light incident portions 13 a to 13 d in the lightguide plate 13 is the anti-reflection surface 13 v. Accordingly, asillustrated in FIG. 4, the light from the position detection lightsources 12A to 12D directly reach the area that is spaced apart from theposition detection light sources 12A to 12D, but it is difficult for thelight reflected from the outer periphery side portions 13 m of the lightguide plate 13 to reach the area. Accordingly, it can be avoided thatthe light emission intensity of the position detection light emittedfrom the area that is spaced apart from the light detection lightsources 12A to 12D becomes heightened in comparison to that of otherareas. In the embodiment of the invention, even in the case where theposition detection method using the intensity distribution of theposition detection light L2 a to L2 d formed by the light guide plate 13is adopted, the position detection light L2 a to L2 d is emitted fromthe light guide plate 13 with an appropriate intensity distribution.Accordingly, in this embodiment of the invention, the position detectioncan be accurately performed.

Particularly, in this embodiment of the invention, since the entiresurface of the outer periphery side portion 13 m except for the lightincident portions 13 a to 13 d is the anti-reflection surface 13 v, thereflection of the position detection light can be prevented on theentire outer periphery portion 13 m. Accordingly, the position detectionlight L2 a to L2 d is emitted from the light guide plate 13 with moreappropriate intensity distribution, and thus the position detection canbe performed more accurately.

Also, in this embodiment of the invention, even in the case where thelight guide plate 13 is in the form of a tetragon or briefly in the formof a tetragonal plane, and the light incident portions 13 a to 13 d areprovided in four corner portions of the tetragon, the position detectioncan be accurately performed. In the case of adopting such aconfiguration, it cannot be avoided that the position detection light L2a to L2 d is headed toward the outer periphery side portion 13 m of thelight guide plate 13. However, according to this embodiment of theinvention, even in the case of using the light guide plate 13 asconfigured above, the reflection of the position detection light doesnot occur in the outer periphery side portion 13 m. Accordingly, theposition detection light is emitted from the light guide plate 13 withan appropriate intensity distribution, and thus the position detectioncan be performed more accurately.

Also, even in the case where two neighboring position detection lightsources among four position detection light sources 12A to 12Dsimultaneously emit the position detection light, the position detectioncan be accurately performed. That is, as illustrated in FIG. 4, if thetwo position detection light sources 12A and 12D simultaneously emit theposition detection light L2 a and L2 d, the light reflected from theouter periphery side portions 13 m of the light guide plate 13 areconcentrated, and thus the intensity distribution of the positiondetection light L2 a to L2 d is remarkably scattered. However, in thisembodiment of the invention, even in the case of adopting such a drivingmethod, the position detection light is emitted from the light guideplate 13 with an appropriate intensity distribution, and thus theposition detection can be performed more accurately.

Also, in this embodiment of the invention, the anti-reflection surface13 v is configured by the light absorption layer 14 formed on the outerperiphery side portion 13 m. Accordingly, it is not necessary to performprocesses that trouble the light guide plate 13 itself, and thus theanti-reflection surface 13 v can be easily formed.

Other Embodiment

The optical position detection apparatus 10 and the display apparatus100 having a position detection function are not limited to theforegoing embodiments, and various modifications may be made withoutdeparting from the scope of the invention. For example, in theabove-described embodiment, although the anti-reflection surface 13 v isconfigured by the light absorption layer 14 formed on the outerperiphery side portion 13 m, the anti-reflection surface 13 v forpreventing the reflection by the light scattering may be configured byforming fine concavo-convexes on the outer periphery side portions 13 m.Also, since the wavelength of the position detection light L2 a to L2 dis constant, the anti-reflection surface 13 v may also be configured byforming a dielectric multi-layer on the outer periphery side portions 13m. In this case, it is sufficient if the light absorption layer 14(anti-reflection surface 13 v) is formed only on a portion of the outerperiphery side portion 13 m except for the light incident portions 13 ato 13 d. Also, in the embodiment of the invention, although only onelight detector 15 is installed, one or more other light detectors may bearranged in an appropriate position.

Modified Example of Display Apparatus 100 Having Position DetectionFunction

In the above embodiment, the configuration including the projection typedisplay apparatus 203, 207 as the image generation apparatus 200 isexplained. However, as shown in FIGS. 5 to 8, if a direct view typedisplay apparatus is employed as the image generation apparatus 200, itcan be used in an electronic apparatus described later with reference toFIGS. 10A and 10B.

Modified Example 1 of Display Apparatus 100 Having Position DetectionFunction

FIG. 5 and FIG. 6 are an exploded perspective view of the opticalposition detection apparatus 10 and the display apparatus 100 havingposition detection function according to the modified example 1 of theinvention, and an explanatory view illustrating a cross-sectionalconfiguration thereof. In the display apparatus 100 having positiondetection function in this embodiment, since the configuration of theoptical position detection apparatus 10 is the same as that of theabove-described embodiment, the common parts are designated with thesame reference symbols and the explanation thereof will be omitted.

The display apparatus 100 having position detection function shown inFIGS. 5 and 6 includes the optical position detection apparatus 10 andthe image generation apparatus 200, and the optical position detectionapparatus 10 includes the position detection light source 12 emittingposition detection light, the light guide plate 13, and the opticaldetector 15 having the light receiving portion 15 a directed to thedetection area 10R. The image generation apparatus 200 is a direct viewtype display apparatus 208 such as an organic electroluminescenceapparatus and a plasma display apparatus, and is disposed opposite tothe input operation side with respect to the optical position detectionapparatus 10. The direct view type display apparatus 208 includes animage display area 20R which is overlapped with the light guide plate 13when seen from the plane, and the image display area 20R overlaps withthe detection area 10R when seen from the plane.

Modified Example 2 of Display Apparatus 100 Having Position DetectionFunction

FIGS. 7 and 8 are explanatory views of the optical position detectionapparatus 10 and the display apparatus 100 having position detectionfunction according to the modified example 2 of the invention. FIG. 7and FIG. 8 are an exploded perspective view of the optical positiondetection apparatus 10 and the display apparatus 100 having positiondetection function according to the modified example 2 of the invention,and an explanatory view illustrating a cross-sectional configurationthereof, respectively. In the display apparatus 100 having positiondetection function in this embodiment, since the configuration of theoptical position detection apparatus 10 is the same as that of theabove-described embodiment, the common parts are designated with thesame reference symbols and the explanation thereof will be omitted.

The display apparatus 100 having position detection function shown inFIGS. 7 and 8 includes the optical position detection apparatus 10 andthe image generation apparatus 200, and the optical position detectionapparatus 10 includes the position detection light source 12 emittingposition detection light, the light guide plate 13, and the opticaldetector 15 having the light receiving portion 15 a directed to thedetection area 10R. The image generation apparatus 200 includes a liquidcrystal apparatus 209 which is a direct view type display apparatus anda light transmissive cover 30. The liquid crystal apparatus 209 includesan image display area 20R which is overlapped with the light guide plate13 when seen from the plane, and the image display area 20R overlapswith the detection area 10R when seen from the plane.

In the display apparatus 100 having position detection function of thisembodiment, an optical sheet 16 is disposed on the light emitting sideof the light guide plate 13 for making the position detection light L2 ato L2 d uniform, as necessary. In this embodiment, as the optical sheet16, a first prism sheet 161 opposing the light emitting surface 13 s ofthe light guide plate 13, a second prism sheet 162 opposing the firstprism sheet 161 on the side opposite to the side where the light guideplate 13 is located, and a light diffusion plate 163 opposing the secondprism sheet 162 on the side opposite to the side where the light guideplate 13 is located. Further, a rectangular frame-like light shieldingsheet 17 is disposed around the optical sheet 16 on the side opposite tothe side where the light guide plate 13 is located with respect to theoptical sheet 16. The light shielding sheet 17 prevents the positiondetection light L2 a to L2 d emitted from the position detection lightsources 12A to 12D from leaking.

The liquid crystal apparatus 209 (the image generation apparatus 200)includes a liquid crystal panel 209 a on the side opposite to the sidewhere the light guide plate 13 is located with respect to the opticalsheet 16 (the first prism sheet 161, the second prism sheet 162, and thelight diffusion plate 163). In this embodiment, the liquid crystal panel209 a is a light transmissive liquid crystal panel and has a structurethat two light transmissive substrates 21 and 22 are bonded by a sealingmaterial 23 and a liquid crystal 24 is filled between the substrates. Inthis embodiment, the liquid crystal panel 209 a is an active matrix typeliquid crystal panel, in which light transmissive pixel electrodes, datalines, scanning lines, and pixel switching elements (not shown) areformed on one of the two light transmissive substrates 21 and 22, andlight transmissive common electrodes (not shown) are formed on the otherthereof. The pixel electrodes and the common electrodes may be formed onthe same substrate. In the liquid crystal panel 209 a, if a scan signalis output via the scanning line for each pixel and an image signal isoutput via the data line, orientation of the liquid crystal 24 iscontrolled in each of a plurality of the pixels, and thus an image isformed in the image display area 20R.

In the liquid crystal panel 209 a, one light transmissive substrate 21is provided with a substrate extension 21 t which is extended to theperiphery from the contour of the other light transmissive substrate 22.Electronic components 25 constituting a drive circuit and the like aremounted on the surface of the substrate extension 21 t. Further, awiring member 26 such as a flexible printed circuit board (FPC) isconnected to the substrate extension 21 t. Only the wiring member 26 maybe mounted on the surface of the substrate extension 21 t. Apolarization plate (not shown) is disposed on the outer surface side ofthe light transmissive substrate 21, 22, as necessary.

Here, in order to detect a plane position of the target object Ob, it isnecessary to emit the position detection light L2 a to L2 d toward theobservation side where operation by the target object Obis performed,and the liquid crystal panel 209 a is disposed closer to the observationside (operation side) than the light guide plate 13 and the opticalsheet 16. Thus, in the liquid crystal panel 209 a, the image displayarea 20R is configured to transmit the position detection light L2 a toL2 d. When the liquid crystal panel 209 a is disposed on the sideopposite to the observation side of the light guide plate 13, it is notnecessary to configure such that the image display area 20R transmitsthe position detection light L2 a to L2 d. However, instead of this, itis necessary to configure such that the image display area 20R can beseen from the observation side through the light guide plate 13.

The liquid crystal device 209 includes an illuminating device 40 forilluminating the liquid crystal panel 209 a. In the present embodiment,the illuminating device 40 is disposed between the light guide plate 13and the reflection plate 14 at the side of the light guide plate 13facing the side where the liquid crystal panel 209 a is located. Theilluminating device 40 includes a light source 41 for illumination and alight guide plate 43 for illumination, which emits illumination lightemitted from the light source 41 for illumination while making theillumination light propagate. The light guide plate 43 for illuminationhas a rectangular flat shape. The light source 41 for illumination isformed by a light emitting element, such as an LED (light emittingdiode), and emits, for example, white illumination light L4 in responseto a driving signal output from a driving circuit (not shown). In thepresent embodiment, a plurality of light sources 41 for illumination isarrayed along a side portion 43 a of the light guide plate 43 forillumination.

In the light guide plate 43 for illumination, an inclined surface 43 gis provided in a surface portion at the light emission side adjacent tothe side portion 43 a (outer peripheral portion of a light emittingsurface 43 s at the side portion 43 a side). The thickness of the lightguide plate 43 for illumination increases gradually toward the sideportion 43 a. By the light incidence structure having the inclinedsurface 43 g, the height of the side portion 43 a is made equal to theheight of the light emission surface of the light source 41 forillumination while suppressing an increase in the thickness of a portionwhere the light emitting surface 43 s is provided.

In this illuminating device 40, the illumination light emitted from thelight source 41 for illumination is incident from the side portion 43 aof the light guide plate 43 for illumination onto the inside of thelight guide plate 43 for illumination, propagates through the inside ofthe light guide plate 43 for illumination toward the outer edge 43 b ofthe opposite side, and then is emitted from the light emitting surface43 s which is one surface. Here, the light guide plate 43 forillumination has a light guide structure in which the ratio of lightamount of light, which is emitted from the light emitting surface 43 s,to internal propagating light, which propagates from the side portion 43a side toward the outer edge 43 b on the opposite side, increasessteadily. For example, this light guide structure is realized bygradually increasing the area of a fine uneven refraction surface forlight deflection or light scattering, which is formed on the lightemitting surface 43 s or the back surface 43 t of the light guide plate43 for illumination, the formation density of the printed scatteringlayer, and the like toward the internal propagation direction. Byproviding such a light guide structure, the illumination light L4incident from the side portion 43 a is emitted almost uniformly from thelight emitting surface 43 s.

In the present embodiment, the light guide plate 43 for illumination isdisposed so as to overlap the image display area 20R of the liquidcrystal panel 209 a in plan view at the opposite side of the viewingside of the liquid crystal panel 209 a, and functions as a so-calledbacklight. However, the light guide plate 43 for illumination may bedisposed at the viewing side of the liquid crystal panel 209 a so as tofunction as a so-called front light. Moreover, although the light guideplate 43 for illumination is disposed between the light guide plate 13and the reflecting plate 14 in the present embodiment, the light guideplate 43 for illumination may also be disposed between the optical sheet16 and the light guide plate 13. In addition, the light guide plate 43for illumination and the light guide plate 13 may be formed using acommon light guide plate. In addition, in the present embodiment, theoptical sheet 16 is commonly used between the position detection lightL2 a to L2 d and the illumination light L4. However, an optical sheetfor exclusive use may also be disposed at the light emission side of thelight guide plate 43 for illumination, separately from the optical sheet16. In this case, a light scattering plate which performs a sufficientlight scattering operation is used in many cases in order to makeuniform the planar luminance of the illumination light L4 emitted fromthe light emitting surface 43 s in the light guide plate 43 forillumination. However, the position detection is interrupted if theposition detection light L2 a to L2 d emitted from the light emittingsurface 13 s in the light guide plate 13 for position detection islargely scattered. For this reason, since a light scattering plate isnot provided or it is necessary to use a light scattering plate whichperforms a relatively slight light scattering operation, it ispreferable that the light scattering plate is a dedicated component ofthe light guide plate 43 for illumination. However, optical sheets witha condensing operation, such as a prism sheet (first or second prismsheet 161 or 162) may be commonly used.

Example of Mounting into an Electronic Apparatus

An electronic apparatus to which the display apparatus 100 having aposition detection function, which has been described with reference toFIGS. 5 to 8, is applied will be described with reference to FIGS. 9A to9C. FIGS. 9A to 9C are explanatory views showing an electronic apparatususing the display apparatus 100 having a position detection functionaccording to the embodiment of the invention. FIG. 9A is a viewillustrating the configuration of a mobile type personal computerincluding a display apparatus 100 having a position detection function.A personal computer 2000 includes the display apparatus 100 with aposition detection function as a display unit and a main body 2010. Apower switch 2001 and a keyboard 2002 are provided in the main body2010. FIG. 9B is a view illustrating the configuration of a mobile phoneincluding the display apparatus 100 having a position detectionfunction. A mobile phone 3000 includes a plurality of operation buttons3001, a plurality of scroll buttons 3002, and the display apparatus 100having a position detection function as a display unit. A screendisplayed on the display apparatus 100 having a position detectionfunction is scrolled by operating the scroll buttons 3002. FIG. 9C is aview illustrating the configuration of a personal digital assistant(PDA) to which the display apparatus 100 having a position detectionfunction is applied. A personal digital assistant 4000 includes aplurality of operation buttons 4001, a power switch 4002, and thedisplay apparatus 100 having a position detection function as a displayunit. By operating the power switch 4002, various kinds of information,such as an address list or a schedule book, are displayed on the displayapparatus 100 having a position detection function.

In addition, examples of an electronic apparatus to which the displayapparatus 100 having a position detection function is applied include adigital still camera, a liquid crystal television, a view finder type ormonitor direct view type video tape recorder, a car navigation system, apager, an electronic diary, an electronic calculator, a word processor,a workstation, a video phone, a POS terminal, a bank terminal, and thelike, as well as those shown in FIGS. 9A to 9C. In addition, the displayapparatus 100 having a position detection function described above maybe applied as a display unit of each of the various kinds of electronicapparatuses.

What is claimed is:
 1. An optical position detection apparatuscomprising: a position detection light source that emits positiondetection light irradiated onto a target object; a light guide platethat receives the position detection light therein and emits theposition detection light above itself; a light detector that receivesthe position detection light; and a signal processing portion that iselectrically connected to the light detector, wherein a side portion ofthe light guide plate has an anti-reflection surface that preventsreflection of the position detection light.
 2. The optical positiondetection apparatus according to claim 1, wherein the side portion ofthe light guide plate has a light incident portion for receiving theposition detecting light.
 3. The optical position detection apparatusaccording to claim 1, wherein a light guide plate receives the positiondetection light therein and emits the received position detecting lightonto a detection area to form an intensity distribution of a lightemission quantity of the position detection light in the detection area.4. The optical position detection apparatus according to claim 1,wherein the light guide plate is shaped as a tetragon, and the lightincident portions are provided in portions corresponding to corners ofthe tetrago.
 5. The optical position detection apparatus according toclaim 4, wherein four position detection light sources are provided, andthe light incident portions are provided on portions that correspond tofour corners of the tetragon shaped light guide plate.
 6. A projectiondisplay apparatus having a position detection function comprising: theoptical position detection apparatus as described in claim 1; and animage projection apparatus that projects the image.